The piston for that band can be removed with the trans in the car.
Replacement of the seal is simple & the band can be adjusted at the same time by measuring the clearance & replacing the "adjustment pin" with the corrected size.
Parts would be less than $20. Would take 2-3 hrs at knowledgable shop.
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)